1. Field of the Invention
This invention relates to a Stirling cycle apparatus or a reverse Stirling cycle apparatus, especially to a Stirling cycle apparatus having a diaphragm which divides a piston back side room and a crank room.
2. Description of Prior Art
A conventional Stirling cycle apparatus, for example a Stirling engine, uses an operational fluid. The operational fluid is cooled or heated and is sent to the expansion cylinder or the compressor cylinder. The expansion cylinder and the compressor cylinder driven by the operational fluid rotate the crank shaft through the piston and the rod. An output shaft connected to the crank shaft supplies the rotational energy as an output power.
A conventional reverse Stirling cycle apparatus, for example a Stirling cycle cooling apparatus or a Stirling cycle compressor, has a motor to rotate the crank shaft. The crank shaft moves the expansion piston and the compressor piston through the rod. The operational fluid in the cylinder is compressed or expanded to take the heat away or to generate the heat.
In this type of Stirling cycle apparatus, a diaphragm dividing the piston back side room and the crank room is attached to the rod which connects the compressor and expansion pistons with the rod. This diaphragm prevents the oil from leak. The volume changes of the piston back side room due to a pressure change may break the diaphragm.
In order to solve this problem, two compressor pistons are placed in 180 degrees to each other and one crank pin is connected to the pistons so that the volume change at the diaphragm has a 180 degree phase difference. Further the piston back side rooms are connected to each other to prevent the volume changes. In this mechanism, however, the torque change in accordance with the movement of the compressor piston is too big and makes too much vibrations and noise. This is due to the arrangement of the two pistons in 180 degrees. The two pistons must be placed in 90 degrees to cut the torque change down. But the load to the diaphragm caused by the volume change of the piston back side room and the crank room becomes another problem. In order to reduce such load, it is easy to use a buffer tank which is connected to the upper room of the diaphragm. It is required, however, a bigger buffer tank to reduce the pressure changes small enough.
The object of the present invention is to provide a Stirling cycle apparatus having improved the above-mentioned drawbacks.
The object of the present invention is to provide a Stirling cycle apparatus has an improved simpler mechanism to reduce the pressure changes to prevent the diaphragm from breaking.
Other objects will be apparent from an understanding of the invention.
In accordance with this invention, a Stirling cycle apparatus comprises of: a cylinder, a compressor piston, an expansion piston, a crank room at the back side of the compressor and expansion pistons, a crank shaft placed in the crank room, a rod connecting the compressor piston with the crank shaft, a rod connecting the expansion piston with the crank shaft, a compressor piston back side room at the back side of the compressor piston, an expansion piston back side room at the back side of the expansion piston, a buffer connecting the compressor piston back side room with the expansion piston back side room, and a diaphragm dividing the buffer and the crank room.
In accordance with the present invention, the pressures at the compressor piston back side room and the expansion piston back side room become the same as the pressure at the buffer. Further, the diaphragm is placed at the rod between the buffer and the crank room so that the pressure changes caused by the volume change between the piston back rooms and the crank room can be absorbed by the diaphragm. The diaphragm at the rod can be moved in accordance with the movement of the rod. Thus the diaphragm is prevented from breaking due to the stress. Further more in this invention, the pressure difference between the upper side of the diaphragm and the lower side of the diaphragm is reduced by a simple mechanism. The stress to the diaphragm is also reduced to make the diaphragm life longer. It will become available to place the piston without considering the pressure changes at the piston back side room and the crank room. Thus the torque change is also reduced.